Cartilage contains a growth promoting factor. The cartilage growth factor (CGF) is a cationic polypeptide with a molecular weight between 17,000 and 18,000 and isoelectric point between 9.0 and 10.0. CGF will stimulate the proliferation of cells of mesenchymal origin such as chondrocytes, endothelial cells, fibroblasts and amniotic fluid cells. CGF is synthesized by chondrocytes and is found to be associated with the chromatin fraction of the nucleus. CGF activity is also found in rat chondrosarcoma. The proposed work includes the following: 1) Purification of CGF to homogeneity on a large scale. 2) Investigating the association of CGF to chromatin and studying the effects of CGF on DNA replication and transcription in vitro. 3) Investigating the uses of CGF as a supplement to medium for improved growth of cells in culture. 4) Raising antibodies to CFG so as to develop radioimmunoassay and immunofluorescence staining techniques. 5) Investigating the role of CGF in cartilage pathology such as arthritis and chondrosarcoma.